This invention relates to semiconductor fabrication processing and more particularly to a structure and process for forming an array of capacitors for a dynamic random access memory device.
The continuing trend of scaling down integrated circuits has forced the semiconductor industry to consider new techniques for fabricating precise components at sub-micron levels. Along with the need for smaller components, there has been a growing demand for devices requiring less power consumption. In the manufacture of transistors, these trends have led the industry to refine approaches to achieve thinner cell dielectric and gate oxide layers.
In dynamic semiconductor memory storage devices it is essential that storage node capacitor cell plates be large enough to retain an adequate charge (or capacitance) in spite of parasitic capacitance and noise that may be present during circuit operation. As is the case for most semiconductor integrated circuitry, circuit density is continuing to increase at a fairly constant rate. The issue of maintaining storage node capacitance is particularly important as the density of dynamic random access memory, (DRAM) arrays continues to increase for future generations of memory devices. The ability to densely pack storage cells while maintaining required capacitance levels is a crucial requirement of semiconductor manufacturing technologies if future generations of expanded memory array devices are to be successfully manufactured.
As disclosed in U.S. Pat. No. 5,418,180, and U.S. Pat. No. 5,407,534, Hemi-Spherical Grain (HSG) silicon enhances storage capacitance when used to form the storage node electrode without increasing the area required for the cell or the storage electrode height.
A disadvantage of using HSG to form a capacitor structure (such as a container type structure) in a deep sub-micron process (a process utilizing is lines width of less than 0.25 microns) is that a small change in the processing conditions may result in the grains of the silicon to overgrow and form discontinuous islands. When the size of the container formation needs to be reduced to such a degree that only a thin film is feasible, the grain formation could quite possibly consume all of the silicon film and form completely isolated grains. Additionally, the space between containers needs to have enough margin to prevent shorts that can be caused by subsequent chemical cleaning. Furthermore, capacitor plate surface enhancement is a function of grain size when HSG is used and a grain size of 700-800 angstroms has been found to provide sufficient surface enhancement. However, a 700-800 angstrom grain size will not fit into a 0.18 xcexcm or less container structured capacitor plate.
The present invention, develops a method to fabricate a capacitor structure for sub-micron fabrication processes. In particular, the present invention provides a capacitor fabrication solution for processes using a device geometry of 0.18 xcexcm or smaller.
U.S. Pat. No. 5,418,180 and U.S. Pat. No. 5,407,534, are hereby incorporated by reference as if set forth in their entirety.
An exemplary implementation of the present invention teaches a process for fabricating a capacitor array for a semiconductor device by forming a first set of individual storage node plates for a first set of storage capacitors; forming a set of storage node pillars, the pillars alternating in position with the individual storage node plates of the first set of individual storage node plates, the storage node pillars being approximately equal in height to neighboring storage node plates. Next, a second set of individual storage node plates are formed so that each individual storage node plate is physically connected to an individual storage node pillar. Next, a cell dielectric material is formed on the first and second sets of individual storage node plates; and finally second capacitor plates are formed over the cell dielectric material and consequently the first and second sets of individual storage node plates.
Another exemplary implementation of the present invention is a memory array comprising conductive word lines running in a generally parallel direction to one another; a first set of individual storage node plates for a first set of storage capacitors; storage node pillars that alternate in position with the individual storage node plates of the first set of individual storage node plates, the storage node pillars being approximately equal in height to neighboring storage node plates; a second set of individual storage node plates for a second set of storage capacitors, each individual storage node plate of the second set physically connecting to an individual storage node pillar; a cell dielectric material on the first and second sets of individual storage node plates; and a second capacitor plate over the first and second sets of individual storage node plates.